The present invention relates generally to pain relief devices and particularly to devices for nerve blocking through transcutaneous application of electric current.
The procedure commonly known as transcutaneous electric nerve stimulation for pain reduction involves the application of electric current to the skin by way of plural electrodes. For certain forms of application it has been found that the effect is more aptly described as a blocking rather than a stimulating action. Such blocking action can provide prolonged pain relief but its effectiveness depends on various characteristics of the stimulating current and electrode placement. In particular it has been shown that waveform characteristics of the stimulating signal can determine results achieved in the reduction of pain. Accordingly, research directed to the optimum stimuli waveform is significant in the area of electrical nerve blocking.
Heretofore, stimulus waveforms have been characterized by bursts of pulses having substantially waxing and waning amplitudes achieved through modulating the amplitude of a pulse signal to provide a burst for each cycle of a modulating envelope. Because the pulse signal and the modulating signal have had no predetermined timed relationship, the waxing and waning characteristics are unpredictable. That is to say, the amplitude of pulses within each burst do not bear a consistent relationship to the amplitude of the burst in which they occur, whereby the amplitude of the first pulse of a given burst can vary widely. As a result, the stimulation can become irritating rather than corrective unless overall signal intensity is limited. The patient can then accommodate or adapt to the corrective signal.